The present invention relates to a control valve for a hydraulic clutch employed in an automobile and other vehicle for an industrial use, an agricultural use and others.
Generally, a control valve system for a hydraulic clutch is designed to control a pressure to be supplied to the clutch according to a speed of a vehicle and an opening degree of a throttle (a stepped-on length of an accelerator pedal). However, a conventional hydraulic control valve system is provided at an oil passage for supplying oil to the clutch with a pair of valves. One of the valves is operable to control the pressure according to the speed of the vehicle. The other is operable to control the pressure according to the opening degree of the throttle. This system including two independent valves has many parts, and thus has a complicated structure. Further, it is difficult to obtain an intended control characteristic when engaging the clutch.
Accordingly, it is an object of the invention to provide an improved control valve having a simple structure and operable to obtain an intended hydraulic characteristic.
The essence of the invention is to provide two pistons in a valve body. One of the pistons is actuated by a force according to a rotation speed of an engine. The other is actuated by a force according to an opening degree of the throttle.